One night, one city, more than a month's worth of rain

ADELAIDE has been drenched overnight with 28.2mm falling since 9am on Sunday, beating the entire average for February in just 24 hours.

And we're set to double the month's average rainfall of 15.4mm as the rain band continues to hover over parts of the state until lunchtime.

The city has copped a total of 29.2mm of rain since 9am on Saturday.

Weather bureau forecaster Matt Bass said the highest rainfall had been at Mt Lofty, which had 38mm of rainfall since 9am Sunday.

"The February average is not really hard to break - one rain event will do it," he said.

"We're probably going to double the average by the end of the day."

He said the rain - while not heavy - would fall "persistently" as a rain band hovers over parts of the state and into Victoria.

Yet despite the wet weather, the heat is on the horizon as South Australia prepares for another stretch of sweltering weather.

While Monday will be soggy with a mild high of 24C, the mercury will begin to climb with temperatures forecast to reach 31C on Tuesday before 40C on Wednesday.

Adelaide will then have three consecutive days of 37C on Thursday, Friday and Saturday before temperatures dip below 30C again on Sunday.

Meanwhile, that same rain band that lashed South Australia over the weekend has forced a plane to be diverted from Melbourne to Adelaide.

Emirates had to divert a flight from Auckland, which was due to land at Melbourne Airport at 8.50pm, to Adelaide due to the torrential downpour.

One person waiting for the plane to arrive took to social media to vent her confusion, saying: "I'm waiting for Aisea's flight from Auckland to arrive in Melbourne and I check the status online and it says it was diverted in-flight and is now in Adelaide."